1. Field of the Invention
The present invention relates to a troubleshooting method of a looped interface and a system provided with a troubleshooting function of the looped interface.
2. Description of the Related Art
For an interface in which devices are connected in a loop such as a Fibre Channel-Arbitrated Loop (FC-AL), as the connection of a cable is simple and correspondence to a network is also easy, such an interface has been often used recently, however, generally, there is a problem that when a signal cannot be normally transmitted in a loop because of a fault and others in an interface circuit of a connected device in an interface of such a type, the whole loop is disabled and all devices connected to the loop are disabled even if the fault is caused in one connected device. As a signal is transmitted from one device to an adjacent device in a loop such as FC-AL, the signal cannot be transmitted ahead from one device in the loop when a fault is caused in the device and when viewed from a port of a fibre channel, the signal is not returned. The transmission of a signal is one-way traffic in a loop.
In case the whole loop is disabled because of a fault in one device, there is a problem that the influence of the fault is large, it also becomes difficult to specify the device in which the fault is caused and it takes much time to analyze the fault and remove the cause.
In an interface of such a type, not only in case a fault is caused in a device but in case a part of a loop is disconnected for example, all connected devices are disabled and it is also difficult to specify a disconnected location.
Recently, a hard disk drive (HDD) with an FC-AL interface has been often used, however, for a countermeasure of a problem that all devices connected to the same loop are disabled when a fault is caused as described above, normally, these devices are respectively provided with interface circuits for two ports so that each device can be connected to two independent loops, a method of enabling access to another loop even if one loop is disabled by a fault is often adopted and hereby, reliability is secured.
As described above, the reliability is enhanced by connecting to two independent interfaces, however, it is unchanged that it is difficult to specify a location of a fault such as a faulty device and a location in which a loop is disconnected, and the analysis and the maintainability are not greatly improved.
The object of the invention is to provide an analysis method to specify a faulty device and a disconnected location which respectively cause the trouble of a link in a system using a looped interface such as a fibre channel which has been recently often used for a disk array and others.
Another object of the invention is to provide a system having high reliability and maintainability a function of which can be recovered by dynamically analyzing a location of a fault and removing the fault if possible.
A troubleshooting method according to the invention is based upon a method of troubleshooting a looped interface used for a system provided with port bypass circuits via which plural devices are connected to a looped interface for detaching the devices from the looped interface and a controller that controls the port bypass circuits and comprises a step in which the controller controls the port bypass circuits and sequentially detaches the device from the looped interface when a link of the looped interface is disconnected, a step for checking whether a loop is faulty after the device is detached or not, a step for acquiring the result of the check by repeating the first and second steps by the number of devices and a step for specifying a device that causes the fault of the loop based upon the result of the check.
Further, a system according to the invention is based upon a system in which plural devices are connected to a looped interface and which is provided with a function for troubleshooting the looped interface and the device, comprises port bypass circuits for detaching the devices from the looped interface and a controller that controls the port bypass circuits, and the controller comprises a detaching unit for controlling the port bypass circuits and sequentially detaching the device from the looped interface when a link of the looped interface is disconnected, a first checking unit for checking whether a loop is faulty after the device is detached or not, a repeated check execution unit for repeating the detachment and the check by the number of the devices to acquire the result of the check and a device specification unit for specifying a device that causes the fault of the loop based upon the result of the check.
As described above, according to the invention, there is not only effect of facilitating the maintenance and the replacement more by specifying a device if the device causes a fault and displaying it so that a maintenance operator can recognize it and but effect of recovering from the fault of a loop by bypassing the device if a composed system has redundancy as a disk array and enabling the recovery of the function of the system. Also, as the range of a part causing a fault can be narrowed even if a device causing the fault cannot be bypassed and the fault is caused in the part having no redundancy, the maintenance can be facilitated more.